PLZ HELP! Reread the underlined sentences. What does the narrator mean? Explain.

"But in an overcrowded and unhappy home, it’s incredibly easy for any child to slip away. The high levels of frustration, depression, and anger in my house made my brother and me invisible. We were children with the sound turned off. And for us, as for the steadily increasing number of neglected children in this country, the only place where we could count on being noticed was at school."